The proposed study represents the first systematic attempt to understand the nature and development of the full range of human food rejections. Human infants reject foods based on taste, or on specific negative expeirences that they have had in connection with ingestion. Adults reject foods on these same grounds, but also reject many substances on ideational grounds. These include items which they believe will cause them some form of personal harm ("dangerous"), substances whose nature and/or origin cause strong emotional rejections ("digust" responses, e.g., feces, worms), and other substances that are considered food, although they do not engender strong emotional responses ("inappropriate," e.g., sand, grass). The first objective of this research is to elaborate and refine the taxonomy described here, through interviews with adults in American culture. The second and primary objective is to study how the ideational rejection arises in development, and how some of them become emotionally charged. In particular, this would include the origin of rejections of body products, "spoiled" foods, and specific taxonomic categories, such as insects. In order to accomplish this prinicipal objective, subsidiary studies will be carried out on food and odor preferences as a function of age, and on the child's conception of food and nutrition, examined within a Piagetian framework. An attempt will be made to relate the origin of disgust responses to toilet training.